As a color printer of an electrophotographic type, a color laser printer including an apparatus main body and a process unit has been known. The process unit holds a plurality of photosensitive members and can be detachably attached to the apparatus main body.
A known example of such a color laser printer is one including a drive source, a main body drive gear, a coupling member, an Oldham member, and a drawer. The drive source is arranged on the apparatus main body. Driving force from the drive source is transmitted to the main body drive gear for rotation drive. The main body drive gear includes the coupling member. The coupling member includes the Oldham member. The drawer supports a photosensitive drum which has a coupling female member on one end.
In the above-described color laser printer, when forming an image, the coupling member is urged by a coil spring and advances toward the coupling female member so that the Oldham member and the coupling female member are engaged with each other. As a result, the coupling member, the Oldham member, and the coupling female member form an Oldham coupling, whereby the main body drive gear and the photosensitive drum are connected and driving force is transmitted to the photosensitive drum.